This invention relates to a two-color copying machine of the type which copies data according to a transfer type heat-sensitve recording system, and more particularly to a two-color copying machine for copying data in two colors; an achromatic color and a particular chromatic color.
A two-color copying machine for copying an original in two colors; an achromatic color and a particular chromatic color, has been proposed in the art. If it is assumed that the particular chromatic color is red, then, in the proposed two-color copying machine, image data in the achromatic color (black) and image data in red on an original are separately read, and the black image data is recorded in black ink while the red data is recorded in red ink, to obtain the image in two colors.
In recording an original, it is impossible to optically separate image data of only a particular chromatic color (red) from other image data. Therefore, heretofore, the light beam passed through the original or reflected from the original has been split into two light beams, and the two light beams then changed in wavelength component from one another by wavelength selection means such as filters. In the case of reading two colors; black and red, a cyan filter, the color of which is complementary to red, is disposed in one optical path, and no filter is disposed in the other optical path.
When red image data is read with this arrangement, in the optical path having the cyan filter, no light passes through the cyan filter and no light is detected by an image sensor on the image forming surface. The same can be said of reading black image data. When image data in any other color is input, the image sensor detects a light beam which has passed through the cyan filter. When light which does not pass through the cyan filter corresponds to image data to be recorded, then the image sensor disposed in this optical path detects the sum of the black (achromatic) and red (chromatic) image data.
On the other hand, in the optical path having no filter, the image sensor detects no light only when the black image data is read. That is, the image sensor in the optical path detects only black (achromatic) image data.
The different image signals from the two image sensors are electrically processed, to obtain a red (chromatic) image signal. Accordingly, the conventional two-color copying machine needs not only two image sensors but also a separating circuit for electrically separating a chromatic color. That is, the conventional two-color copying machine is disadvantageous in that the image data reading mechanism is intricate and expensive.